用桥面补强层加固中小跨径钢筋混凝土板桥

用桥面补强层加固中小跨径板桥,是在凿除旧桥面铺装层和铰缝混凝土后,用相同厚度的钢筋混凝土桥面补强层取代旧桥面铺装,补强层和新铰缝混凝土同时浇筑成为一体,并使它们与原有梁板形成整体。该法不增加桥梁自重,同时铰缝得到改善并和补强层成为一体,故加固效果更为明显。在修复桥面的同时,使桥梁的承载能力得到提高。列举了湖州市公路养护工程实例,证明该法可解决中小跨径钢筋混凝土铰接板桥承载能力不足和桥面病害反复维修的问题。     

Enhancing the fire resistance of composite floor assemblies through the use of steel fiber reinforced concrete

This paper presents a strategy for achieving the required fire resistance in composite floor systems through the use of steel fiber reinforced concrete (SFRC). Both experimental and numerical studies were carried out to evaluate the fire performance of floor systems comprising unprotected steel beams and concrete/SFRC deck slabs. The results from these studies show that SFRC composite deck slabs develop significant tensile forces (through tensile membrane action) that transfer load from fire-weakened steel beams to other cooler parts of the structure. Preliminary results indicate that the combined effect of composite construction, tensile membrane action, and the improved properties of SFRC under realistic fire, loading, and restraint conditions can provide sufficient fire resistance in steel beam-concrete deck slabs without the need for external fire protection on the floor assembly.     

大跨加劲弦钢桁梁桥减小桥面系共同作用技术措施研究

对跨度为(112 208 112)m宽幅加劲弦钢桁架梁桥的桥面系参与主桁架共同作用引起的横梁水平弯曲这一突出问题进行详细地分析,按照把纵梁和平纵联施工分为:随施工顺序同步连接、桥面板放置前连接和分段滞后连接等3种不同的方案,分别计算横梁水平弯曲应力和组合应力,并对计算结果进行比较,由此得出结论:纵梁和平纵联分段滞后连接方案为相对可行的施工方案。     

对组合钢梁-预制空心板中栓钉连接件的性能分析

在钢-混凝土组合梁中,剪切连接件的机械作用使得纵向剪力转移到钢翼缘/混凝土板的接合处。这种转移能力取决于剪切连接件的强度和混凝土板抵抗由剪力高度集中所导致的纵向开裂的能力。大多数对组合结构的分析都集中在传统的钢筋混凝土和金属面板结构,而对预制空心板中栓钉的剪切能力研究很少。本文对带栓钉的预制空心板组合梁结构提出标准的推力试验方法。一共进行7组测试性试验,试验结果显示新方法符合钢筋混凝土楼板规范要求。在确定这个新的标准方法后,对栓钉进行了72个足尺推力试验,确定了该类型连接件的性能,通过分析试验结果,还指出了各类参数对连接件强度和延性的作用。本文还提出了这种剪力连接件的设计公式。     

Öresund Bridge. Temperature and cracking control of the deck slab concrete at early ages

High performance features are required of the concrete for the deck slab of the bridge over Öresund Straight between Denmark and Sweden and, among them, great durability. To guarantee this, it is necessary to assure, in advance, and control during the construction of the deck slabs, that the maximum temperatures and the traction stresses in the deck slab will not be greater than the allowable values, and to control these factors during the construction process. Before beginning construction, the deck slab was calculated using a program of finite elements that considers the heat generated, the shrinkage and creep of the concrete and the ambient conditions. To control the temperature during construction, temperature sensors are installed in various sections of each of the 49 deck spans and the temperatures produced during the first days of hardening are recorded on a computer. The temperatures of the components are also measured in order to estimate the temperature of the fresh concrete.     

组合楼板的最新发展——钢纤维网片混凝土承板组合楼板

众所周知 ,组合楼板的承载力主要取决于钢板 -混凝土界面处的抗剪强度 ,而许多因素影响抗剪强度。现在美国开发出一种新型组合板形式 :钢纤维网片混凝土承板———SIMCON承板组合楼板 ,性能优越 ,有大力推广的潜力     

Capacities of headed stud shear connectors in composite steel beams with precast hollowcore slabs

In steel-concrete composite beams, the longitudinal shear force is transferred across the steel flange/concrete slab interface by the mechanical action of the shear connectors. The ability of the shear connectors to transfer these longitudinal shear forces depends on their strength, and also on the resistance of the concrete slab against longitudinal cracking induced by the high concentration of shear force. Most of the research in composite construction has concentrated on the more traditional reinforced concrete and metal deck construction, and little information is given on shear capacity of the headed studs in precast hollowcore slabs. In this paper, a standard push test procedure for use with composite beams with precast hollowcore slabs is proposed. Seven exploratory push tests were carried out on headed studs in solid RC slabs to validate the testing procedures, and the results showed that the new test is compatible with the results specified in the codes of practice for solid RC slabs. Once a standard procedure is established, 72 full-scale push tests on headed studs in hollowcore slabs were performed to determine the capacities of the headed stud connectors in precast hollowcore slabs and the results of the experimental study are analysed and findings on the effect of all the parameters on connectors’ strength and ductility are presented. Newly proposed design equations for calculating the shear connectors’ capacity for this form of composite construction are also be given.     

Behavior of Steel–Concrete Partially Composite Beams Subjected to Fire—Part 1: Experimental Study

Partially composite steel–concrete beams are commonly used in building construction, and so the behavior of such beams in fire is an important problem. This paper presents the results of an experimental investigation on the response of two composite beam specimens subject to fire exposure. The two specimens were nominally identical, except for the shear connection ratio. Based on room temperature calculations, one specimen was designed as fully composite, and the second was designed as partially composite with a 50% shear connection ratio. The concrete slab for each specimen was constructed with a flat steel deck and reinforcement was provided by a reinforcing bar truss. Both specimens were subject to a constant vertical load applied at four locations along the span and tested in a furnace with an ISO-834 standard fire. Both specimens achieved large deflections associated with flexural yielding of the composite beams and exhibited measured flexural capacities larger than predicted from Eurocode 4. Based on test measurements, the shear connection ratio had a significant influence on interface slip and uplift behavior of concrete slabs. Failure of the specimens was defined when the maximum deflection reached span/30. The fire exposure time needed to reach this definition of failure was nearly the same for both specimens, and was 51 min for the fully composite beam and 49 min for the partially composite beam. A companion paper considers the degradation of material properties with temperature and slips behavior of shear connectors at elevated temperatures and also provides an analytical approach to predict fire response of steel–concrete partially composite beams.     

GFRP筋混凝土桥面板承载性能的试验研究

为了研究采用玻璃纤维筋（GFRP）作为配筋材料的混凝土桥梁面板工作性能,结合板内的压缩薄膜效应对该类结构进行了静力加载试验研究。在试验设计中采用了一套1∶3比例缩小的试验模型,桥梁面板分别支撑于混凝土梁和钢梁上。通过改变结构模型参数,包括支撑梁尺寸、配筋率和配筋材料等,分析其对GFRP筋混凝土桥梁面板承载性能的影响。将试验结果与现行FRP筋混凝土结构设计规范（ACI440.1R06）对比后发现,现行设计规范低估了该结构的真实承载能力。为了准确计算出该非金属筋材混凝土结构的实际承载力,建立了非线性有限元模型,该数值模型的计算结果与试验结果有着良好吻合。     

悬挂式钢-混住宅结构体系的研究

悬挂式钢-混结构体系是适应跃层建筑的新型结构体系,并适应了建筑大开间大空间要求,主体结构均为异形柱框架,单数层楼盖为大开间钢筋混凝土楼盖,双数层为轻钢结构楼盖。为了提高建筑净空高度,减小钢梁截面,可灵活设置钢吊杆,悬挂在主体结构上,从而形成了一种新型结构体系———悬挂式钢-混结构体系。该结构体系需要通过结构试验及计算理论试点工程深入论证确认。     

Strengthening concrete beams for shear with CFRP sheets

The method of strengthening concrete structures with FRP composites has existed for over a decade; the most common way to strengthen structures is in bending, but also wrapping of columns is quite common. There are also needs for strengthening concrete structures in shear, for example concrete beams, slabs, columns, etc. A typical structure can be a parking garage. However, strengthening concrete structures for shear is not as common as for bending and confinement. This paper presents examples to strengthen concrete beams for shear. First traditional strengthening methods are presented briefly, then the use of CFRP (Carbon Fibre reinforced Polymers) composites for shear strengthening is presented. Tests on beams strengthened in shear with CFRP sheets are presented and a short presentation on how to design for shear strengthening with CFRP is given. Furthermore, a field application of a parking slab strengthened for shear with CFRP unidirectional fabric is presented. The laboratory tests show the importance of considering the principal directions of the shear crack in relation to the unidirectional fibre. The field application shows that it is easy to strengthen existing structures for shear with CFRP fabrics.     

单层单跨钢框架抗火性能的试验研究

本文对2榀H型钢单层单跨钢框架进行抗火性能的试验研究。试验采用足尺试件,钢梁长3400mm,钢柱高3200mm,混凝土板宽1000mm。试验中考虑不同受火工况对钢框架抗火性能的影响。通过试验得出了梁、板、柱温度场变化规律和钢框架变形情况。试验结果表明:火灾下,由于钢筋混凝土板的存在,钢梁沿截面高度各点温度不一致,即钢梁沿截面高度存在温度变化的温度场;梁柱全部受火的单层单跨钢框架(节点受到保护)破坏方式为钢柱压屈破坏,破坏位置在受到保护的钢节点下部的钢柱上。本文研究结果为今后钢结构抗火性能的进一步研究提供参考数据。     

钢-混凝土双面组合连续梁截面刚度试验研究

钢-混凝土组合梁是在钢结构和钢筋混凝土结构基础上发展起来的一种新型结构。当采用连续组合梁时,负弯矩区会出现钢梁受压、混凝土翼板受拉的不利情况,使混凝土桥面板因承受较大拉应力而开裂,引起钢筋及钢梁腐蚀等严重问题,影响结构的承载能力和耐久性。而双面组合梁(在传统的单面组合梁的内支座负弯矩区设置下翼缘钢筋混凝土板)能够很好地改善单面组合梁的这种不利受力状态。通过采用简化计算方法对双面组合梁截面刚度进行计算,与试验实测值进行了对比分析。     

Experimental study on semi-rigid composite joints with steel beams and precast hollowcore slabs

The concept of semi-rigid composite connection has been widely researched in the past; however, most of the researches are limited to composite joints with metal deck flooring and solid concrete slabs. Composite construction incorporating precast concrete hollowcore slabs (HCU) is a recently developed composite floor system for buildings. The research on the structural behaviour of the semi-rigid composite joints with HCU is new and without any previous experimental database. In this paper, eight full-scale tests of beam-to-column semi-rigid composite joints with steel beams and precast hollowcore slabs are reported. The variables are stud spacing, degree of the shear connections, area of the longitudinal reinforcement and slab thickness. The test set-up and instrumentation is described in detail. The experimental behaviour is analysed and based on the test data the structural behaviour of these semi-rigid composite joints is discussed. Based on the experimental data, a simplified method to predict rotation and moment capacity for this type of composite connection is proposed.     

Fire tests on two-way concrete slabs in a full-scale multi-storey steel-framed building

This paper presents the results from two full-scale furnace tests conducted on two-way concrete slabs supported by composite beams in a three-storey steel-framed building. Each floor of the building consisted of nine panels (three by three) supported by composite beams. In two tests, a corner and an interior panel on the top of the building were heated by two specially designed furnaces respectively. Detailed experimental data in the form of describing slab cracking, the furnace temperatures, temperature distributions within the slab, vertical deflections and horizontal displacements are presented. Comparison of the results for the two tests indicates that the structural fire behaviour of two-way concrete slabs supported by composite beams in a multi-storey steel-framed building is highly dependent on the restraint provided by the adjacent structural members. Observations from the tests indicate that in addition to the extensive cracks formed on the top surface of the heated panels, regular cracks also occurred on the top of the adjacent unheated panels due to structural continuity and the interaction between the concrete slabs and the supporting beams. The test results show that both tested panels had good fire performances even under long duration fire conditions.     

预应力混凝土梁板正截面计算中的问题

给出了有效预应力水平σpe不同时常规预应力混凝土梁板相对界限受压区高度的限值,为合理考虑预应力筋有效预应力水平对常规有粘结预应力混凝土梁板正截面承载力的影响提供依据。提出了FRP筋预应力混凝土梁板设计应遵循的原则和具体设计的方法。     

压型钢板—混凝土组合楼板受弯性能的试验研究

进行了 6个足尺寸压型钢板—混凝土组合板的受弯性能试验 ,探讨压型钢板厚度、混凝土板厚度、混凝土强度等级等参数对组合板弯曲受力性能的影响 ,得出若干有用结论 ,并建立组合板受弯承载力计算的实用公式。     

Testing of full-scale concrete bridge deck slabs reinforced with fiber-reinforced polymer (FRP) bars

This paper presents an experimental study investigating the behavior of FRP-reinforced concrete bridge deck slabs under concentrated loads. A total of eight full-scale deck slabs measuring 3000-mm long by 2500-mm wide were constructed. The test parameters were: (i) slab thickness (200, 175 and 150 mm); (ii) concrete compressive strength (35–65 MPa); (iii) bottom transverse reinforcement ratio (1.2–0.35%); and (iv) type of reinforcement (GFRP, CFRP, and steel). The slabs were supported on two parallel steel girders and were tested up to failure under monotonic single concentrated load acting on the center of each slab over a contact area of 600 × 250 mm to simulate the footprint of sustained truck wheel load (87.5 kN CL-625 truck). All deck slabs failed in punching shear. The punching capacity of the tested deck slabs ranged from 1.74 to 3.52 times the factored load (P_f) specified by the Canadian Highway Bridge Design Code (CHBDC) CAN/CSA S6-06. Besides, the ACI 440.1R-06 punching strength equation greatly underestimated the capacity of the tested slabs with an average experimental-to-predicted punching capacity ratio (V_exp/V_pred) of 3.17.     

收缩对混凝土组合板长期应力与变形的影响

混凝土板和钢面板组合而成的单向板常作为永久模板在建筑结构中得到广泛应用。钢面板在浇筑混凝土时作为模板,待混凝土凝固后作为外部加固构件。这类板的使用性能具有时间依赖性,目前对其研究较少,在计算长期变形时为结构工程师提供的指导也较少。众所周知,板底部的不透水钢面板对沿组合板板厚分布的混凝土干燥收缩特性有着重要影响,但该影响尚未被量化。通过试验测定了沿组合板板厚非均匀分布的收缩特性,考虑了该结果对这类板长期变形的影响。组合板的应力与变形随时间变化而变化,该文描述了确定组合板应力和变形的分析过程,通过所测量的收缩特性,给出几种常见板型的分析结果。     

水泥混凝土桥双层SMA桥面铺装关键施工工艺

为提高水泥混凝土桥双层SMA桥面铺装的施工质量,从桥面板的处理、桥面板不平度以及双层SMA铺装的碾压工艺研究等几个方面,对水泥混凝土桥双层SMA桥面铺装的关键施工工艺进行了研究,并提出了针对性的改进措施,从而提高桥面铺装质量。